1. Field of the Invention
The present invention relates to tools for use in oil wells. More particularly, the invention relates to methods and apparatus for supplying treatment fluid to a wellbore casing of an oil well.
2. Description of the Prior Art
The problem addressed by the present invention is how to maintain a producing oil well in operating condition for extended periods of time without the need for replacing the downhole well tubing or casing. In a producing oil well, chemicals, which typically produce scale buildup and are corrosive to steel used to manufacture the oil well casing, are pumped from the well formation through perforations formed in the casing.
The chemicals circulated through the well casing, at the relatively high temperatures encountered, can eventually corrode the casing or cause scale buildup, which substantially restricts the flow of oil through the casing. Once these problems occur, the well then has to be taken out of production and the entire casing replaced at great expense in time and lost production.
Treatment fluid is available to impede scale buildup and the corrosion process. Other treatment fluids which reduce viscosity and inhibit wax buildup are also available. The prior art does not include any showing wherein treatment fluid is slowly released with the chemicals being circulated through the well formation and the casing.
No prior art is known which shows a flexible bladder to eject treatment fluid into a wellbore by means of compressing the bladder with a piston-like weight. W. H. Boles (U.S. Pat. No. 219,440) discloses a means for venting pressure from a beer barrel. This vent functions in a manner to keep a constant pressure in the barrel. A weight is used to force air out of a bag and into the beer barrel to maintain a constant static pressure within the barrel.
Prior art patents for cleaning wellbores by discharge of chemical fluids include A. M. Herbsman (U.S. Pat. No. 2,089,479) and J. D. Haynes (U.S. Pat. No. 2,543,068). Both Herbsman and Haynes disclose means for dumping fluids into wellbores. Both use a piston to discharge fluid into the wellbore. Herbsman uses a tubular barrel having a plunger slideable there along and a releaseable dump valve. Herbsman therefore disgorges the entire contents of the barrel, which are contemplated to be potassium or sodium, into a well formation adjacent the bottom of the casing.
In a like manner to Herbsman, Haynes uses a container to hold a quantity of liquid material to be deposited in the oil well. The outside diameter of the container is less than that of the wellbore. A piston mechanical means is used to move the piston to discharge the liquid contents of the container.